Glossary of Morphological and Anatomical Terms

dalliniform - Loop arrangement typical of adult Dallina in which long descending lamellae recurve into ascending lamellae that meet in transverse band all free of the valve floor.
delayed costation - Ribbing that first arises in postneanic stages of shell growth.
deltarium discretum - Thickened edge of delthyrium.
delthyrial angle - Angle subtended by margins of delthyrium.
delthyrial callosity - See pedicle callist.
delthyrial carinae - See teeth ridges.
delthyrial cavity - See delthyrial chamber.
delthyrial chamber - Cavity beneath umbo of ventral valve bounded by dental plates if present, or by posterolateral shell walls, if dental plates absent.
delthyrial foramen - Foramen in young shells.
delthyrial plate - Plate within delthyrial chamber of some spiriferides, extending variable distance from apex between dental plates (probably homologue of pedicle collar).Fig.355_1.
delthyrium - Median triangular or subtriangular aperture bisecting ventral cardinal area or pseudointerarea commonly serving as pedicle opening.Fig.283.
deltidial cover - Externally concave plate in some pentameroids closing posterior end of delthyrium (probably homologue of pedicle collar).
deltidial grooves - Lines delimiting thecideidine pseudodeltidium in species with this structure not flush with ventral area.
deltidial plates - Two plates growing medially from margins of delthyrium partly or completely closing it.Fig.316.
deltidial ridges - Two narrowly triangular ridges separating homeodeltidium and propareas of trimerelloids.
deltidiodont - Simple hinge teeth developed by distal accretion of secondary shell.Fig.322.
deltidium - Cover of delthyrium formed by conjunct deltidial plates line of junction of plates visible.Fig.317.
deltiform - Terminal loop phase typical of many short-looped terebratulides with a variably disposed transverse band extending between the distal ends of two relatively short, divergent, descending lamellae.
dental cavity - Anteriorly expanding cavity, presumably occupied by evagination of outer epithelium secreting the tooth of some atrypoids.
dental flange - Internal border and buttress to delthyrium and teeth in spiriferides, not extending to valve floor.Fig.324.
dental lamellae - See dental plates.
dental plates - Variably disposed plates of secondary shell underlying hinge teeth and extending to floor of ventral valve.Fig.323.
dental sockets - Excavations in posterior margin of dorsal valve for reception of hinge teeth.Fig.323.
dental valve - See ventral valve.
denticles - Small, protruding ridges that alternate with complementary sockets located along cardinal margin or hinge line of both valves; also small processes on posterior surfaces of dental sockets fitting into accessory sockets in hinge teeth.Fig.325.
denticular cavities - Pair of grooves on outer side of teeth that receives projections from outer socket ridges.Fig.322.
denticular plates - Pair of obtusely triangular plates lateral to delthyrium bearing denticles and fused with dental plates developed in strophodontids.
denticulated cardinal margin - Posterior margin of both valves bearing denticles fitting into complementary sockets.
denticulated commissure - Zigzag commissure due to interfingering of angular ribs.Fig.300.
denticulum - Small toothlike termination of cardinal area usually in ventral valve, commonly articulating with accessory socket in outer socket ridge.Fig.322.
dentifer - Vestigial brachiophore in some orthotetidines; See brachiophore.
depth - See thickness.
descending branches - See descending lamellae.
descending lamellae - Paired dorsal elements of loop extending anteriorly from crura and recurved ventrally at anterior ends.Fig.338.
deuterolophe - Spirally coiled part of lophophore bearing double brachial fold and double row of paired tentacular appendages, homologous with side arms of plectolophe.Fig.337.2,4,5,6.
diaphragm - Extension of visceral disk commonly as marginal ridge of productide and strophomenide dorsal valve maintaining a close fit with ventral valve and usually associated with trails.
dictyothridid stage - See parasulcate.
diductor muscles - Muscles serving to open valves of articulated brachiopods, commonly consisting of two pairs attached to dorsal valve immediately anterior to beak usually to cardinal process principal pair commonly inserted in ventral valve on either side of adductor muscles and accessory pair posterior to them.Fig.348.
digitate - Posterior part of vascula genitalia projecting laterally nearly to mantle margin with corresponding abbreviation of vascula myaria.Fig.379,Fig.380.
diploform - Phase of loop development, typical of adult Campages, with adjacent ascending and descending elements fused, well developed, and free of the septum except at their posterior extremities.Fig.334.
disjunct deltidial plates - Plates not in contact anterodorsally of pedicle.
divaricator muscles - See diductor muscles.
divided hinge plates - Plates not united medially.
dorsal - Direction toward dorsal valve.
dorsal adjustor muscles - See adjustor muscles.
dorsal adminicula - See adminicula.
dorsal denticulum - See outer socket ridge.
dorsal foramen - Posteriorly located perforation of cardinal plate which may encroach on beak of dorsal valve.Fig.359.
dorsal valve - Valve that invariably contains any skeletal support for lophophore and never wholly accommodates pedicle commonly smaller than ventral valve and with distinctive muscle-scar pattern.Fig.283.
dorsibiconvex - Dorsal valve more convex than ventral valve.
dorsiconvex - See dorsibiconvex.
dotted brachial ridges - Ridges of thecideoid brachidium represented by rows of small, separate pustules.
double deltidial plates - Pair of deltidial plates each of which is seen in certain transverse sections to consist either of two parallel plates or of one plate nearer hinge line buttressed by another disposed at angle to it.
double median septum - More or less elevated median plate in pentameride dorsal valve formed by union of two septal plates.
double-barrelled spine - External spine of primary shell having oval to subquadrangular cross section and commonly barbed, bearing variably closed suture on commissural surface and, at least proximally, a median partition so that spine scars are bipartite.Fig.306.
dyscoliid stage - Probably a trocholophe.